Прегледај по Аутор "Miličić, Dragan"

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    Influence of Welding Speed on Fracture Toughness of Friction StirWelded AA2024-T351 Joints
    (MDPI, 2021) Milčić, Miodrag; Miličić, Dragan; Vuherer, Tomaž; Radović, Ljubica; Radisavljević, Igor; Đurić, Aleksija
    In order to ensure a quality welded joint, and thus safe operation and high reliability of the welded part or structure achieved by friction stir welding, it is necessary to select the optimal welding parameters. The parameters of friction stir welding significantly affect the structure of the welded joint, and thus the mechanical properties of the welded joint. Investigation of the influence of friction stir welding parameters was performed on 6-mm thick plates of aluminum alloy AA2024 T351. The quality of the welded joint is predominantly influenced by the tool rotation speed n and the welding speed v. In this research, constant tool rotation speed was adopted n = 750 rpm, and the welding speed was varied (v = 73, 116 and 150 mm/min). By the visual method and radiographic examination, imperfections of the face and roots of the welded specimens were not found. This paper presents the performed experimental tests of the macro and microstructure of welded joints, followed by tests of micro hardness and fracture behavior of Friction StirWelded AA2024-T351 joints. It can be concluded that the welding speed of v = 116 mm/min is favorable with regard to the fracture behavior of the analysed FSW-joint.
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    MULTI-OBJECTIVE OPTIMIZATION OF THE RESISTANCE SPOT-WELDING PROCESS PARAMETERS FOR THE WELDING OF DUAL-PHASE STEEL DP500
    (Institute of Metal Materials and Technologies, 2021) Đurić, Aleksija; Miličić, Dragan; Klobčar, Damjan; Marković, Biljana
    Resistance spot welding (RSW) is still the most used form of welding in the automotive industry, primarily for welding steel. One of the advanced steels used in the automotive industry is dual-phase steel, so it is important to properly select the welding parameter for these steels. Therefore, this paper presents multi-objective optimization in the RSW welding process of DP 500 steel. The paper considers three different mechanical characteristics i.e., the failure load (F), failure displacement (l) and weld nugget diameter (D), as all these welding characteristics play significant roles in evaluating the quality of spot welding. The results show that the welding current is the most influential parameter with respect to the mechanical characteristics. The effect of welding time on the weld quality is the least significant. The optimal parameters for welding DP 500 steel obtained in this paper are weld current 8 kA, electrode force 4.91 kN and weld time 400 ms.